Spaceflight-Associated Brain White Matter Microstructural Changes and Intracranial Fluid Redistribution

Importance: Spaceflight results in transient balance declines and brain morphologic changes; to our knowledge, the effect on brain white matter as measured by diffusion magnetic resonance imaging (dMRI), after correcting for extracellular fluid shifts, has not been examined. Objective: To map spaceflight-induced intracranial extracellular free water (FW) shifts and to evaluate changes in brain white matter diffusion measures in astronauts. Design, Setting and Participants: We performed retrospective, longitudinal analyses on dMRI data collected between 2010 and 2015. Of the 26 astronauts’ dMRI scans released by the National Aeronautics and Space Administration Lifetime Surveillance of Astronaut Health, 15 had both preflight and postflight dMRI scans and were included in the final analyses. Data were analyzed between 2015 and 2018.